People with typical eyesight perceive depth of field while viewing three dimensional objects. They also rely on their depth of field perception when they undertake ordinary, commonplace activities such as driving a car, walking down the street, and playing sports. Most people closely associate their ability to perceive depth with reality. However, the majority of computer images, digitally generated images, movies and television programs are viewed as a series of two-dimensional images. While viewing computer images, digitally generated images, movies and television programs in two dimensions, the audience does not experience a realistic three-dimensional, stereoscopic perspective. Viewing movies and television programs in this three-dimensional perspective gives the viewer an additional element of reality.
For a person with normal eyesight, perceiving depth of field is achieved by close interactions between the person's nerve endings, brain, and eyes. When viewing an object, the right eye perceives a slightly different image than the left eye. This slightly different image between the right eye and left eye is normal because the right and left eyes reside in different locations relative to the object being viewed. The nerve endings of each eye perceive the right image and left image of the right and left eye, respectively. The nerve endings then transmit these images to the brain. The brain utilizes both the right and left images to produce a depth of field or stereoscopic perspective for the person viewing the object. These interactions occur very rapidly and appear naturally to the viewer.
There are numerous prior devices that attempt to provide viewers with a stereoscopic perspective while viewing a two-dimensional image. For example, U.S. Pat. Nos. 3,802,769 and 4,012,116 both only provide a stereo-effect image for still images. Further, both of these references require the viewers to be located at a center location relative to each device in order to experience the stereo-effect image. Accordingly, since each device is not attached to the viewer, these devices fail to provide the viewer with the stereo-effect image, once the viewer changes position such that the viewer is no longer aligned with the center of the device; it is unreasonable to expect an average viewer to remain motionless so that these types of applications are only temporarily effective. In addition, these devices taught by U.S. Pat. Nos. 3,802,769 and 4,012,116, only display still images. As a result, these devices have very limited applications.
Other stereoscopic viewers utilize polarizing filters to display right and left images to each corresponding eye of the user. For example, U.S. Pat. Nos. 4,623,219, 4,719,507, and 4,744,633, teach the use of polarizing filters to display stereoscopic, animated images. In these references, one image is modulated by linearly polarized high intensity light. The other image is modulated by an orthogonally disposed component of the above linearly polarized high intensity light. The viewers wear polarized glasses to allow each eye to view the respective left and right images. These systems suffer the drawback of only being effective for three-dimensional viewing when the image has been specially encoded for left and right images. Further, the use of these polarizing filters decreases the efficiency of the system because a portion of the light waves are lost in the decoding process. This decrease in efficiency results in images that lack the more vivid qualities of unfiltered images.
Three-dimensional glasses, with one red lens and one blue lens, are also very well known. Similar to the polarizing filters discussed above, this technique utilizes color filter so that one image is modulated by blue light waves and the other image is modulated by red light waves. This suffers similar drawbacks of the polarizing filters described above which include the need to encode a left image and a right image and the loss in efficiency because the left and right images need to be decoded. Further, because of the colored lenses, the viewer cannot perceive natural, balanced colors.
Some stereo viewing devices use two full displays. One display is provided for each of the user's eyes. Each of the display is provided with the appropriate data for forming the image that would naturally be seen by that one of the user's eye. Such a system adds cost due to duplication of display and light sources. Additionally, it has been observed that errors in registration between the displays, errors in focus, color and update rates of the two displays relative to one another can disorient or nauseate a user.
What is needed in a low cost method and apparatus of producing appropriate stereo images for a user's left and right eyes which are uniform and eliminates optical errors. What is needed is a device which displays three-dimensional stereoscopic images from a two-dimensional image source. What is further needed is a device which allows the user to view three-dimensional stereoscopic images without utilizing filters and while allowing the user to move freely. What is further needed is a device that does not expose the viewer to potentially harmful radiation from a cathode ray tube.